By Tom Balmforth

(Reuters) -Ukrainian President Volodymyr Zelenskiy said on Thursday the Russian missile that struck a residential building in Kyiv overnight and killed 12 people was supplied by North Korea, confirming an earlier Reuters report.

A North Korean KN-23 (KN-23A) missile hit a residential block in the Sviatoshynskyi district west of Kyiv's centre during a major aerial attack by Russia, a Ukrainian military source told Reuters.

"According to preliminary information, the Russians used a ballistic missile manufactured in North Korea. Our special services are verifying all the details," Zelenskiy said on X, without providing further details.

Russia made no comment on Zelenskiy's remarks. Russia and North Korea have denied weapons transfers that would violate U.N. embargoes.

Russia's military cooperation with North Korea grew rapidly as Moscow became internationally isolated after invading Ukraine in February 2022.

Ukraine says North Korea has supplied Russia with vast amounts of artillery shells as well as rocket systems, thousands of troops and ballistic missiles, which Moscow began using for strikes against Ukraine at the end of 2023.

By the start of 2025, Pyongyang had supplied Russia with 148 KN-23 and KN-24 ballistic missiles, Ukraine's military spy agency says.

KN-23 (KN-23A) missiles are armed with warheads of up to one tonne, which is more powerful than the Russian equivalent missiles, the Ukrainian source said.

In the initial readout after the Russian attack, Kyiv said seven ballistic missiles were used in total, identifying them broadly as Iskander-M/KN-23.

North Korea's involvement in Ukraine has alarmed not only European capitals but also South Korea and its allies in Asia, who fear that lessons learned from war could be unleashed on them one day.

(Reporting by Tom Balmforth; additional reporting by Sergiy Karazy and Yuliia Dysa; editing by Alex Richardson, Philippa Fletcher and Cynthia Osterman)